384 Dr. J. Shields on Hydrolysis 



If we start at the point where the mixture is neutral we 

 may construct the following table, from which we can calcu- 

 late the quantity of free alkali in the solution at the point of 

 apparent neutrality. This quantity, as has already been sug- 

 gested, is perhaps due to the hydrolysis of hydrogen disodium 

 phosphate ; whilst the quantity of free alkali determined by 

 direct titration is due to the presence of trisodium phosphate, 

 formed according to the equation 



2Na 2 HP0 4 = Na 3 P0 4 + NaH 2 P0 4 . 



The influence of the dihydrogen sodium phosphate has been 

 neglected altogether. 



t 



C 2 — x. 



X. 



C-x. 









4-76 



o-oo 



48-70 





27 



4-70 



0-06 



48-64 





115 



4-66 



o-io 



48-60 



64X10- 8 



221 



4-61 



015 



48-55 



(86) 



375 



4-59 



0-17 



48-53 



65 



1375 



4-46 



0-30 



48-40 



59 



2810 



4-35 



0-41 



48-29 



55 



4495 



4-24 



052 



48-18 



54 









Mean 



= 59xl0~ 8 



- 



K=0-00000236. 



A=0'000033, or 0'07 per cent, of salt hydrolysed. 



The amount of free alkali determined by direct titration is 

 0*63 per cent., whilst that determined from the velocity of 

 saponification, starting at the' neutral point, is 0*07 per cent. ; 

 it is therefore evident that the total amount of free alkali in 

 the solution is very small when compared with what is present 

 in a solution of trisodium phosphate. 



Sodium Acetate, 



After having estimated the amount of hydrolysis in salts 

 of strong bases with some of the weakest acids, it was 

 thought desirable to extend the experiments a little and 

 determine the amount of hydrolysis in a salt of a stronger 

 acid, for example acetic acid. For this purpose a tenth 

 normal solution of sodium acetate was prepared and investi- 

 gated in the same manner as the salts of the weaker acids. 

 The calculation of the results, however, was in this case much 

 simplified, owing to the fact that the concentrations of the salt 

 and ester did not alter much during the reaction, consequently 



